1. Field of the Invention
This invention relates to resettable circuit interrupting devices, and more particularly to a ground fault circuit interrupter (GFCI) device with self-test and remote annunciation capabilities.
2. Description of the Related Art
Ground fault circuit interrupters (GFCIs) were developed to meet a need for a device that is capable of detecting abnormal current flow (typically from phase to ground) and consequently interrupt power to the electrical system in which the fault occurred. In such a manner the device protects persons from electric shock, fire etc. Detection of ground fault currents in the order of milliamps may be detected, concurrent with load currents such as 10 to 100 amps. Thus, in the absence of a ground fault, the GFCI can enable connection of alternating current (AC) power to downstream electrical loads and receptacle outlets. When a ground fault is detected, the GFCI can open contacts to disconnect the AC power to the load.
When a ground fault is detected, a GFCI can interrupt both phase and neutral lines. Users are thus protected from phase to ground faults even if the phase and neutral wires are inadvertently switched. However miswiring of the GFCI can cause a loss of protection for some receptacles (wall outlets). Receptacle GFCIs can be wired to protect a “single outlet,” or they can be wired as “through” devices to protect the face outlet of the GFCI and outlets downstream. In new construction GFCIs will typically be installed prior to electricity being applied. This can result in a possible miswiring, as the wiring box contains two pairs of phase and neutral wires which are not easily identifiable as line and load. Consequently, there is a possibility that an installer might inadvertently connect the line side of the AC wiring to the load side of the GFCI which may create a potential hazard.
In addition to miswiring, GFCIs also may be subject to other failure modes. These failure modes may be caused by abnormal operating conditions such as poor AC supply quality, misuse or chemical action upon the GFCIs parts. To ensure reliable operation, GFCI devices can incorporate a TEST button, on the exterior of the GFCI device, that when pressed, causes the contacts to open and power is removed from the electrical circuit protected by the GFCI. Following a test, the GFCI can be reset to its normal operating condition by pressing a RESET button, on the exterior of the GFCI that, when pressed, simulates a ground fault. This simulated ground fault causes the internal circuitry to respond as if a real ground fault has occurred. Internal components, circuitry and mechanical mechanisms are thereby exercised and tested. If the internal mechanisms of the GFCI are working correctly, the circuit interrupter contacts close and power is restored to the receptacles. Users may be instructed to test the GFCI periodically and replace devices that fail. However, users may not test their GFCIs on a regular basis, if at all, even when visible instructions are placed on the GFCI itself.
GFCI reliability also may be compromised by a power outage and the corresponding surge when power is restored. Power restoration can cause large electrical spikes of voltage and current to appear on the power line, thus creating a possibility of GFCI component failure. Therefore, a GFCI should be tested subsequent to power restoration.
Commercial buildings and industrial/administrative complexes, with multiple floors generally may have many GFCIs. For example, GFCIs may be located in bathrooms, at utility sinks, kitchen areas and outside receptacle outlets. Multiple building complexes such as a campus, a government building complex, corporate center etc. can have hundreds of such GFCI areas for protection of personnel from shock hazards. Testing of GFCIs to ensure proper function may present a logistical problem when testing a large number of GFCIs, for example in a large building or industrial/administrative complex. If a sufficient number of GFCIs are involved, personnel may be permanently employed to press the TEST and RESET buttons on GFCI's and ensure that all the GFCI's are tested on a regular basis, such as monthly. Also the recording of which GFCIs have been tested, and which have not, can become a large undertaking prone to errors and miscommunication.
To assure protection of personnel from shock hazards due to ground faults, GFCIs in residential and commercial environments must be correctly installed and GFCI regularly tested.